Fabrication of an Aurin Tricarboxylic Acid Immobilized Chelating Polymer for the Ion Chromatographic Determination of Trace Metal Ions in Highly Mineralized Waters

Abstract

A high efficiency 7 µm neutral polystyrene divinylbenzene resin, impregnated with the chelating dye aurin tricarboxylic acid (ATA), was investigated for the separation and quantitative determination of Cd(II), Pb(II) and Cu(II) in high ionic strength matrices including mineral waters, by chelation ion chromatography. The fabricated ATA substrate demonstrated a unique selectivity pattern for transition and heavy metal ions, being more selective towards the environmental pollutants Cd(II) and Pb(II) in particular, in comparison with dyes containing iminodiacetate groups which have been extensively investigated recently. A development of the dye impregnation procedure, using ultrasound, siginificantly increased the capacity of the chelating column by a factor of four. Utilising a developed pH gradient elution, in an eluent of 0.1 M potassium nitrate to suppress ion exchange interactions, allowed Cd(II), Pb(II) and Cu(II) to be baseline resolved from other transition metals and the alkaline earths within 30 min. Detection limits were considerably improved by buffering the 4-(2-pyridylazo)resorcinol post column reagent with borate instead of ammonia, resulting in a threefold increase in sensitivity for Cd(II) and near twofold for Pb(II) at 520 nm. The developed procedure was applied to the determination of these metals in highly mineralised water and high ionic strength matrices. The calibration curves produced good linearity (>0.994), with excellent detection limits of 1 µg L⁻¹ for Cd(II) and 5 µg L⁻¹ for both Pb(II) and Cu(II), respect vely.

Keywords:

• Ion chromatography
• Chelation
• Aurin tricarboxylic acid
• Metal ions
• Cadmium
• Lead